Variable capacity compressor

ABSTRACT

A variable capacity compressor includes: cylinder bores; a drive shaft; a rotor fixed with the drive shaft; a link for linking the rotor and a journal; a tilting plate capable of changing its tilted angle; and pistons capable of reciprocating within the cylinder bores along with a rotation of the tilting plate. Each reciprocating stroke of the pistons is adjusted according to the tilted angle of the tilting plate. The link is linked with the rotor via a first pivot and linked with the journal via a second pivot. An arrangement of the first and second pivot is set so that each head clearance of the pistons decreases as a discharge capacity decreases toward its minimum value within a small discharge capacity range. According to the compressor, it can be prevented that the discharge flaw amount is cut off abruptly and the tilted angle can be sustained stably.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable capacity compressor forvarying its discharging capacity of a piston by adjusting a tilted angleof a tilting plate (swash plate, wobble plate).

2. Description of Related Art

A conventional variable capacity compressor is disclosed in JapanesePatent Application Laid-Open Number 2006-233855.

As shown in FIG. 5, the variable capacity compressor 100 includes ahousing 101. The housing 101 is assembled primarily of a cylinder block101 a, a front head 101 b provided at one end of the cylinder block 101a and a rear head 101 c provided at another end of the cylinder block101 a via a valve plate 102.

A drive shaft 103 is provided at the center of the housing 101. Bothends of the drive shaft are rotatably supported by the housing 101 viaradial bearings 104 and 105.

Within the cylinder block 101 a, cylinder bores 106 are formed on acircumference with the drive shaft 103 as the center. A piston 107capable of reciprocating is provided in each of the cylinder bores 106.A crank chamber 108 is provided within the front head 101 a, whichcommunicates with the cylinder bores 106. Within the crank chamber 108,provided are a rotor 109 fixed on an outer circumferential surface ofthe drive shaft 103, a sleeve 110 provided slidably on the outercircumferential surface of the drive shaft 103, a journal 112 providedoutside the sleeve 110 and linked with the rotor 109 via a link 111 anda tilting plate 113 fixed on an outer circumferential surface of thejournal 112. The pistons 107 are coupled to an outer circumference ofthe tilting plate 113 via pairs of shoes 114. First and second springsS1 and S2 are provided at both sides of the sleeve 110. The tiltingplate 113 will be returned to its initial position due to a balancebetween elastic forces of the first and second springs S1 and S2 after ashutdown.

On the drive shaft 103 rotating, the pistons 107 are reciprocated withinthe cylinder bores 106, respectively, due to the rotor 109, the tiltingplate 113 and so on. A reciprocating stroke amount of the pistons 107 isvaried due to a tilted angle of the tilting plate 113.

A suction chamber 120 and a discharge chamber 121 are provided withinthe rear head 101 c.

The valve plate 102 is interposed between the cylinder head 101 a andthe rear head 101 c. Therefore, the cylinder bores 106 and the chambers120 and 121 are partitioned by the valve plate 102.

According to the above-mentioned configuration, the tilting plate 113swings to reciprocate the pistons 107 on the drive shaft 103 beingrotated. Refrigerant is supplied into the cylinder bore 106 from thesuction chamber 120 during a suction stroke of the piston 107. Thesupplied refrigerant is compressed and discharged into the dischargechamber 121 during a compression stroke of the piston 107. Thedischarged refrigerant is circulated in a refrigerating cycle to beserved for air-conditioning or the like and returned to the capacityvariable compressor 100.

A pressure in the crank chamber 108 is made low when thermal load forthe refrigerating cycle becomes large during the capacity variablecompressor 100 driving. As a result, a balance will be disrupted betweena counter-clockwise moment (to move the tilting plate 113 in FIG. 5) dueto a crank chamber pressure (a back pressure of the pistons 107) and theelastic force of the first spring S1 and a clockwise moment due to afront pressure of the pistons 107 and the elastic force of the secondspring S2. Thereby, the clockwise moment becomes large to increase thetilted angle of the tilting plate 113, so that the link 111 swings in anarrowed direction a in FIG. 5 until the both moments are balanced. (Asecond pivot 111 b is moved in the arrowed direction a from a smallcapacity state [FIG. 7] to a large capacity state [FIG. 5].) Suchswinging of the link 111 makes the tilted angle of the tilting plate 113large. The reciprocating stroke amount of the pistons 107 turns to belarge when the tilted angle of the tilting plate 113 is made large.Thereby, a discharge amount of the refrigerant is made large, so that acooling performance or the like is enhanced.

On the other hand, the pressure in the crank chamber 108 is made highwhen the thermal load for the refrigerating cycle becomes small. As aresult, the balance will be disrupted between the counter-clockwisemoment due to the crank chamber pressure (the back pressure of thepistons 107) and the elastic force of the first spring S1 and theclockwise moment due to the front pressure of the pistons 107 and theelastic force of the second spring S2. Thereby, the counter-clockwisemoment becomes large to decrease the tilted angle of the tilting plate113, so that the link 111 swings in an arrowed direction b in FIG. 5until the both moments are balanced. (The second pivot 111 b is moved inthe arrowed direction b from the large capacity state [FIG. 5] to thesmall capacity state [FIG. 7].) Such swinging of the link 111 makes thetilted angle of the tilting plate 113 small. The reciprocating strokeamount of the pistons 107 turns to be small when the tilted angle of thetilting plate 113 is made small. Thereby, the discharge amount of therefrigerant is made small, so that the cooling performance or the likeis reduced. The capacity variable compressor 100 conserves energyaccording to the above-mentioned operation.

In addition, the rotor 109 and the journal 112 are connecting each otherwith the link 111 as shown in FIGS. 6A and 6B in the conventionalcapacity variable compressor 100. Such a linkage with the link 111 canserve lower frictions than a linkage with an elongate hole and a pinslidable within the elongate hole. Note that the link 111 is provided ina pair and a first pivot 111 a is also provided in a pair as shown inFIGS. 6A and 6B. However, they are referred as the “link 111” and the“first pivot 111 a” hereinafter.

SUMMARY OF THE INVENTION

However, with respect to the first pivot 111 a (connecting the rotor 109and the link 111) and the second pivot 111 b (connecting the journal 112and the link 111), the first pivot 111 a is arranged near the rotor 109(on the side of the rotor 109) and the second pivot 111 b is arrangednear the journal 112 (on the side of the journal 112) in theabove-mentioned conventional capacity variable compressor 100.Therefore, with respect to head clearance, there is a tendency indicatedby a characteristic line of a conventional example in FIG. 4 at a timewhen the tilted angle of the tilting plate 113 is small (within a smalldischarge amount range of the piston 107) as shown in FIG. 7. Then, thehead clearance increases as the capacity decreases toward its minimumvalue. Since stroke becomes small as a matter of course, dead volumeratio to the discharge amount increases drastically. As a result, adischarge flow amount from the cylinder bores 106 is cut off abruptly asa certain tilted angle. Since the small discharge amount range isbasically an unstable range due to a small discharge amount, the tiltedangle of the tilting plate 113 cannot be sustained stably when thedischarge flow amount changes rapidly as mentioned above.

An object of the present invention is to provide a capacity variablecompressor that can restrain a sudden cut-off of the discharge flowamount within the small discharge amount range as much as possible andcan sustain the tilted angle of the tilting plate stably.

An aspect of the present invention is to provide a capacity variablecompressor that includes a housing within which a plurality of cylinderbores and a crank chamber communicating with the plurality of cylinderbores are provided; a drive shaft rotatably supported within thehousing; a rotor fixed with the drive shaft; a link for linking therotor and a journal; a tilting plate capable of changing a tilted anglethereof by a movement of the journal; and a plurality of pistons capableof reciprocating within the plurality of cylinder bores, respectively,due to a swinging rotation of the tilting plate. The tilted angle of thetilting plate is changed due to a rotation of the rotor by way of thelink. Each reciprocating stroke of the plurality of pistons is adjustedaccording to the tilted angle of the tilting plate. The link is linkedwith the rotor via a first pivot and linked with the journal via asecond pivot. An arrangement of the first and second pivot is set sothat each head clearance of the plurality of pistons decreases as adischarge capacity decreases toward a minimum value thereof within asmall discharge capacity range.

According to the above aspect of the present invention, since the headclearance reduces as the capacity decreases toward its minimum valuewithin the small discharge capacity range, it can be prevented as muchas possible that the discharge flaw amount is cut off abruptly and thetilted angle of the tilting plate can be sustained stably.

It is preferable that a ratio of a head clearance B at the top deadcenter of the piston to a stroke A of the piston shall be defined as astroke ratio B/A, and the arrangement of the first and second pivot isset so that the stroke rate B/A is made constant or decreases as thedischarge capacity decreases within the small discharge capacity range.

According to this, since the stroke rate is made constant or decreasesas the capacity decreases within the small discharge capacity range ofthe pistons, it can be prevented firmly that the discharge flaw amountis cut off abruptly and the tilted angle of the tilting plate can besustained stably.

It is also preferable that the link is configured so that the firstpivot is arranged nearer to the journal than the second pivot and thesecond pivot is arranged nearer to the rotor than the first pivot.

According to this, since the head clearance reduces as the capacitydecreases toward its minimum value within the small discharge capacityrange, it can be prevented as much as possible that the discharge flawamount is cut off abruptly and the tilted angle of the tilting plate canbe sustained stably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall cross-sectional view of a variable capacitycompressor according to an embodiment of the present invention;

FIG. 2A is a plan view of a linkage in the variable capacity compressoraccording to the embodiment of the present invention;

FIG. 2B is a side view of the linkage in the variable capacitycompressor according to the embodiment of the present invention;

FIG. 3A is an explanatory diagram showing a stroke ratio under a midcapacity setting;

FIG. 3B is an explanatory diagram showing a stroke ratio under a smallcapacity setting;

FIG. 4 is a characteristic line chart showing relations between adischarge capacity and a head clearance in the variable capacitycompressor according to the embodiment of the present invention;

FIG. 5 is an overall cross-sectional view of a conventional variablecapacity compressor;

FIG. 6A is a plan view of a linkage in the conventional variablecapacity compressor;

FIG. 6B is a side view of the linkage in the conventional variablecapacity compressor; and

FIG. 7 is a cross-sectional view of primary elements when a stroke iszero.

DETAILED DESCRIPTION OF THE EMBODIMENT

Hereinafter, one embodiment according to the present invention will beexplained with reference to drawings.

As shown in FIG. 1, a variable capacity compressor 1 includes a housing2. The housing 2 is configured to be assembled of a cylinder block 2 a,a front head 2 b provided at one end of the cylinder block 2 a and arear head 2 c provided at another end of the cylinder block 2 a via avalve plate 3.

A drive shaft 4 penetrating an after-mentioned crank chamber 10 isprovided within the cylinder block 2 a and the front head 2 b. Both endsof the drive shaft 4 are rotatably supported by the cylinder block 2 aand the front head 2 b via radial bearings 5 and 6. One end of the driveshaft 4 is projected outward from the front head 2 b and a pulley 7 isfixed on the projected end to receive engine rotation. The drive shaft 4is configured to rotate by receiving a drive force from the pulley 7fixed on its one end.

Cylinder bores 8 are formed within the cylinder block 2 a. The cylinderbores 8 are formed at even intervals on a circumference with the driveshaft 4 as the center. A piston 9 capable of reciprocating is providedin each of the cylinder bores 8.

The crank chamber 10 is provided within the front head 2 b, whichcommunicates with the cylinder bores 8. Within the crank chamber 10,provided are a rotor 11 fixed on an outer circumferential surface of thedrive shaft 4, a sleeve 12 provided slidably on the outercircumferential surface of the drive shaft 4, a journal 13 providedoutside the sleeve 12, a link 14 connecting the journal 13 and the rotor11, a tilting plate 15 fixed on an outer circumferential surface of thejournal 13 and rear ends of the pistons 9, each coupled to an outercircumference of the tilting plate 15 via a pair of shoes 16.

An outer circumferential surface of the sleeve 12 is formed almostspherical to smoothly guide a transition of the tilted angle of thetilting plate 13. First and second springs S1 and S2 are provided atboth sides of the sleeve 12. The tilting plate 15 will be returned toits initial position due to a balance between elastic forces of thefirst and second springs S1 and S2 after a shutdown. A linkage with thelink 14 will be explained later in detail.

On the drive shaft 4 rotating, its rotation is transmitted to thetilting plate 15 by the rotor 11, the link 14 and the journal 13 toreciprocate the pistons 9 within the cylinder bores 8. In addition, eachstroke of the pistons 9 is varied due to the tilted angle of the tiltingplate 15 to change a discharge amount of refrigerant. Mechanism foradjusting the tilted angle of the tilting plate 15 will be explainedlater.

A suction chamber 20 and a discharge chamber 21 for refrigerant gas areprovided within the rear head 2 c. The suction chamber 20 is connectedto an outlet of an evaporator in a refrigerating cycle. The dischargechamber 21 is connected to an inlet of a condenser in the refrigeratingcycle. In addition, the cylinder bores 8 and the chambers 20 and 21 arepartitioned by the valve plate 3. Discharge holes 22 are provided on thevalve plate 3 within partitioning areas between the bores 8 and thedischarge chamber 21. A discharge valve is provided at each of thedischarge holes 22. Suction holes (not shown) are provided on the valveplate 3 within partitioning areas between the bores 8 and the suctionchamber 20. A suction valve (not shown) is provided at each of thesuction holes.

Further, an extraction path (not shown) is provided between the crankchamber 10 and the suction chamber 20, which is always opened. An intakepath 23 is provided between the crank chamber 10 and the dischargechamber 21. A pressure control valve 24 is provided on the intake path23. The pressure control valve 24 is configured to control a pressurewithin the crank chamber 10 by adjusting its valve opening.

Next, the linkage with the link 14 will be explained. As shown in FIGS.1, 2A and 2B, the link 14 is connected with the rotor 11 via the firstpivot 14 a and connected with the journal 13 via the second pivot 14 b.The first pivot 14 a is arranged near the journal 13 (on the side of thejournal 13) and the second pivot is arranged near the rotor 11 (on theside of the rotor 11). Namely, the link 14 is linked with thearrangement of the first and second pivot 14 a and 14 b being reversedas compared with the above-mentioned conventional example. According tothe linkage, head clearance decreases as the capacity (tilted angle)decreases toward its minimum value within a small discharge amount rangeof the pistons 9 (equal-to or less-than 40% capacity, equal-to orless-than 8 degrees tilting plate angle) as shown by a characteristicline of the present invention in FIG. 4.

A ratio of a head clearance B at the top dead center (TDC) of the piston9 to a stroke A of the piston 9 shall be defined as a stroke ratio B/A,as shown in FIG. 3. In the present embodiment, with respect to adecreasing tendency of the head clearance, the arrangement of the firstand second pivots 14 a and 14 b is set so that the stroke rate is madeconstant or decreases as the capacity decreases within the smalldischarge capacity range of the piston 9.

In the above configuration, on the drive shaft 4 rotating, the tiltingplate 15 rotates due to the rotational force of the drive shaft 4. Then,the pistons 9 reciprocate within the cylinder bores 8. During thesuction stroke of the pistons 9 (stroke from TDC to BDC), the suctionholes (not shown) are opened due to a pressure reduction within thecylinder bores 8. As a result, the refrigerant gas is supplied from thesuction chamber 20 to cylinder bores 8.

During the compression stroke of the pistons 9 (stroke from BDC to TDC),the suction holes (not shown) are closed and the refrigerant gas withinthe cylinder bores 8 is compressed adiabatically by the pistons 9. Thecompressed refrigerant gas with high-temperature and high-pressure isdischarged from the discharge holes 22 to the discharge chamber 21. Thedischarged refrigerant gas with high-temperature and high-pressure isdischarged from the capacity variable compressor 1 via the outlet port(not shown). The discharged refrigerant gas is circulated in therefrigerating cycle to be served for air-conditioning or the like andreturned to the capacity variable compressor 1 again.

A pressure in the crank chamber 10 is made low when thermal load for therefrigerating cycle becomes large during the capacity variablecompressor 1 driving. As a result, a balance will be disrupted between acounter-clockwise moment (to move the tilting plate 15 in FIG. 1) due tothe crank chamber pressure (a back pressure of the pistons 9) and theelastic force of the first spring S1 and a clockwise moment due to afront pressure of the pistons 9 and the elastic force of the secondspring S2. Thereby, the clockwise moment becomes large to increase thetilted angle of the tilting plate 15, so that the link 14 swings in anarrowed direction a in FIGS. 1 and 2B until the both moments arebalanced. (The second pivot 14 b is moved in the arrowed direction afrom the small capacity state toward the large capacity state [FIG. 1].In FIG. 1, the second pivot 14 b is already moved to the limit of thearrowed direction a.) Such swinging of the link 14 makes the tiltedangle of the tilting plate 15 large. The reciprocating stroke amount ofthe pistons 9 is made large when the tilted angle of the tilting plate15 is made large. Thereby, a discharge amount of the refrigerant is madelarge, so that a cooling performance or the like is enhanced.

On the other hand, the pressure in the crank chamber 10 is made highwhen the thermal load for the refrigerating cycle becomes small. As aresult, the balance will be disrupted between the counter-clockwisemoment due to the crank chamber pressure (the back pressure of thepistons 9) and the elastic force of the first spring S1 and theclockwise moment due to the front pressure of the pistons 9 and theelastic force of the second spring S2. Thereby, the counter-clockwisemoment becomes large to decrease the tilted angle of the tilting plate15, so that the link 14 swings in an arrowed direction b in FIGS. 1 and2B until the both moments are balanced. (The second pivot 14 b is movedin the arrowed direction b from the large capacity state [FIG. 1] towardthe small capacity state.) Such swinging of the link 14 makes the tiltedangle of the tilting plate 15 small. The reciprocating stroke amount ofthe pistons 9 turns to be small when the tilted angle of the tiltingplate 15 is made small. Thereby, the discharge amount of the refrigerantis made small, so that the cooling performance or the like is reduced.The capacity variable compressor 1 conserves energy according to theabove-mentioned operation.

Next, explained will be an operation within the small discharge amountrange of the pistons 9. Within the small discharge amount range of thepistons 9, the head clearance is made smaller as the capacity (tiltedangle) decreases toward its minimum value. Therefore, it can beprevented firmly that the discharge flaw amount is cut off abruptly andthe tilted angle of the tilting plate 15 can be sustained stably.

In the present embodiment, since the arrangement of the first and secondpivots 14 a and 14 b is set so that the stroke rate is made constant ordecreases as the capacity decreases within the small discharge capacityrange of the piston 9, it can be prevented firmly that the dischargeflaw amount is cut off abruptly and the tilted angle of the tiltingplate 15 can be sustained stably. Specifically, the stroke rate ishardly influenced even if the head clearance B is somewhat large withina mid discharge capacity range as shown in FIG. 3A because the stroke Ais large. However, the stroke rate is greatly influenced by alterationof the head clearance B within the small discharge capacity range asshown in FIG. 3B because the stroke A is small. Therefore, within thesmall discharge capacity range, the refrigerant discharge may be cut offabruptly if the stroke rate became large. However, since the stroke rateis set not more than a certain value in the present embodiment, it canbe prevented firmly that the discharge flaw amount is cut off abruptly.

1. A variable capacity compressor comprising: a housing within which aplurality of cylinder bores and a crank chamber communicating with theplurality of cylinder bores are provided; a drive shaft rotatablysupported within the housing; a rotor fixed with the drive shaft; a linkfor linking the rotor and a journal; a tilting plate capable of changinga tilted angle thereof by a movement of the journal; and a plurality ofpistons capable of reciprocating within the plurality of cylinder bores,respectively, due to a swinging rotation of the tilting plate; whereinthe tilted angle of the tilting plate is changed due to a rotation ofthe rotor by way of the link, each reciprocating stroke of the pluralityof pistons is adjusted according to the tilted angle of the tiltingplate, the link is linked with the rotor via a first pivot and linkedwith the journal via a second pivot, and an arrangement of the first andsecond pivot is set so that each head clearance of the plurality ofpistons decreases as a discharge capacity decreases toward a minimumvalue thereof within a small discharge capacity range.
 2. The compressoraccording to claim 1, wherein a ratio of a head clearance B at the topdead center of the piston to a stroke A of the piston shall be definedas a stroke ratio B/A, and the arrangement of the first and second pivotis set so that the stroke rate B/A is made constant or decreases as thedischarge capacity decreases within the small discharge capacity range.3. The compressor according to claim 1, wherein the link is configuredso that the first pivot is arranged nearer to the journal than thesecond pivot and the second pivot is arranged nearer to the rotor thanthe first pivot.